Integrated UV–H2O2 and biological treatment processes for the removal of cationic surfactant

Abstract

Surfactants are widely used for industrial and domestic purposes although these chemicals are potentially harmful to the environment. This research work reports the degradation of cetyltrimethylammonium bromide (Ctab), a representative cationic surfactant present in waste waters, using an integrated ultraviolet (UV)–hydrogen peroxide (H2O2) and biological treatment process. The toxicity of raw Ctab and partially (50%) UV–hydrogen peroxide-treated Ctab samples were analysed using zebra fish as the model organism. The LC50 values of raw and 50% degraded Ctab samples at 24 h exposure were found to be 4.89 and 2.13 mg/l, respectively, and these indicated that partially degraded Ctab samples were less toxic. The biodegradability index of the degraded samples was found to increase along with the amount of UV–hydrogen peroxide treatment. The treatability of degraded Ctab solution was studied in an aerobic sequential batch reactor (bioreactor) for different sludge ages. The biokinetic parameters (k S, k, Y and K d) for the partially degraded sample were evaluated using a modified Monod equation. The study indicated that the partially advanced-oxidation-process-degraded Ctab samples can be effectively removed by a biological process.